Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A COATING COMPOSITION AND A REFLECTIVE COATING SYSTEM
LNCL LTDING SAME
RELATED APPLICATIONS
[0001]
FIELD OF THE INVENTION
[0002] The present
invention generally relates to a coating composition and,
more specifically, to a reflective coating system including a cured film that
is formed
from the coating composition and disposed on a substrate. The cured film is
transparent and has excellent solar reflectivity and corrosion resistance.
DESCRIPTION OF THE RELATED ART
[0003] Coil coating
compositions are known in the art and are typically
applied to a substrate, e.g, a metal substrate, to form a cured film prior to
an end use
of the substrate. Typical end uses of the substrate include appliances,
automotive
parts and assemblies and architectural applications. More specifically, the
coil
coating compositions are commonly utilized when the substrate is utilized in
an
architectural application, such as roofing or a gutter, in a residential or a
commercial
building. The cured film is employed to provide both aesthetic and energy
conservation properties to the substrate and, when the substrate is the metal
substrate,
the cured film is also employed to passivate the metal substrate, thereby
providing
resistance to corrosion.
[0004] The selection
of the coil coating composition is dependent upon many
desired characteristics and properties of the cured film formed from the coil
coating
composition, such as solar reflectivity properties, emissivity properties,
anti-corrosion
properties, anti-weathering properties, ultraviolet protection properties and
aesthetics.
[0005] Solar
reflectivity is typically referred to as an albedo (a) value and is
generally a measure of an ability to reflect sunlight, including visible,
infrared, and
ultraviolet wavelengths of the sunlight. The albedo value is a ratio of
reflected solar
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radiation flux to incident flux and quantified as a value of from 0.0 to 1Ø
An albedo
value of 0.0 denotes a total absorption of the sunlight while an albedo value
of 1.0
signifies a total reflectivity of the sunlight. To qualify as Energy Star
efficient under
Environmental Protection Agency guidelines, the albedo value must be greater
than or
equal to 0.65 for roofing having no substantial slope (typically commercial
buildings),
and greater than or equal to 0.25 for roofing having a slope (typically
residential
buildings). When the albedo value is high, e.g. approaching 1.0, a thermal
gain of the
residential or commercial building due to exposure to sunlight is reduced.
Thermal
gain is a temperature increase within the building on which the roofing is
located,
which is caused when the roofing does not reflect sunlight, or solar
radiation.
Therefore, it is advantageous for cured films formed from the coil coating
composition to have a high albedo value, and thus a maximized solar
reflectivity.
[0006]
Emissivity (c) is generally a measure of energy radiation. Emissivity is
typically defined as a ratio of energy radiated by an object to energy
radiated by a
black body at the same temperature and is quantified as a value of from 0.0 to
1Ø A
black body is an object that absorbs all electromagnetic radiation that
strikes the black
body, i.e., the black body does not reflect electromagnetic radiation. The
emissivity
of most metals is typically low, e.g. approximately 0.20 for aluminum. While
there is
no emissivity standard mandated by the Environmental Protection Agency for an
Energy Star rating, the emissivity of roofs of residential or commercial
buildings is
preferably high, e.g. approaching 1.0, to reduce the thermal gain in the
residential or
commercial building from the sunlight. As such, it is advantageous to maximize
the
emissivity of cured films formed from coil coating compositions. When the
emissivity of the cured films is maximized, the costs to cool the residential
and/or
commercial building are reduced. In addition, when the emissivity is
maximized, a
"heat island" effect is reduced, which causes increased temperatures in urban
locations.
[0007] Coil
coating compositions typically include a resin, a cross-linking
agent, a solvent (or water), and one or more additive components contingent on
physical properties desired of the cured film formed from the coil coating
composition. The resin is usually selected based upon consideration for
resistance to
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weathering, chemicals, dirt, and other natural elements while remaining
flexible when
formed into the cured film.
[0008] Chromate
is typically included in coil coating compositions and aids in
passivation of the metal substrate. Chromate is a strong oxidizing agent and,
in the
presence of water, forms insoluble compounds that prevent and chemisorptively
bind
corrosion-promoting ions, thereby protecting the metal substrate from
corrosion.
Chromate also imparts the coil coating composition, as well as the cured film
formed
therefrom, with excellent adhesion to the metal substrate. Excellent adhesion
of the
cured film to the metal substrate is difficult to attain when the metal
substrate is
formed from certain metals. However, chromate is a volatile organic compound
(VOC) and is potentially carcinogenic. As such, there is a need for safer
alternatives
with similar desirable properties to those of chromate.
[0009] In
addition to chromate, the coil coating compositions typically include
a color pigment, which is employed to adjust functional and aesthetic aspects
of the
coil coating compositions and the cured films formed therefrom. When the color
pigment is incorporated into the coil coating compositions, the color pigment
typically
imparts the cured films formed from the coil coating compositions with a
color.
When the end use of the metal substrate is roofing, the color is typically
selected for
aesthetic reasons, because it is often desirable for roofing to have a
particular color
and match other structures of the commercial or residential buildings.
However, the
color has a functional justification as well, because when the color of the
cured film is
lighter, the roofing will have a higher albedo value and, thus, reduced
thermal gain.
The color pigment of the coil coating contributes to an opacity of the' cured
film
formed therefrom, which inhibits the appearance of the metal substrate from
exhibiting through the cured film. However, in several applications, such as
roofing
for commercial buildings, it may be desirable to retain the appearance of the
metal
substrate.
[0010] When the
cured films are transparent, the roofing is protected from
corrosion and weathering. However, traditional cured films that are
transparent do
not have a high albedo value or solar reflectivity and, as such, contribute to
increased
costs to cool the commercial building on which the roofing is located.
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[0011] In view
of foregoing, it would be advantageous to provide an improved
coating composition that can be applied to a substrate to form a cured film
having a
solar reflectivity such that the cured film meets Energy Star efficiency
standards. It
would be further advantageous to provide an improved coating composition
addressing the deficiencies set forth above.
SUMMARY OF THE INVENTION AND ADVANTAGES
[0012] The
present invention provides a coating composition. The coating
composition is substantially free from chromate, and comprises a resin, a
metal salt,
and an interference pigment. The interference pigment comprises mica having a
solar
reflective coating disposed thereon. This invention also provides a reflective
coating
system comprising a cured film formed from this coating composition. In this
reflective coating system, the cured film is disposed on a substrate and has a
transparency of at least 75%, as measured according to ASTM 1746.
[0013] The
coating composition of the present invention is substantially free
from chromate yet still has substantially similar physical properties to
conventional
coating compositions which do include chromate, including excellent adhesion
to the
substrate and corrosion resistance. The coating composition forms a cured film
that is
transparent, as noted above. As such, the substrate of the reflective coating
system
retains the appearance of the substrate even with the cured film disposed
thereon.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The
present invention provides a coating composition. The coating
composition may be applied on a substrate to form a cured film. The present
invention also provides a reflective coating system, which comprises the cured
film
formed from the coating composition disposed on the substrate. The reflective
coating system may be used in applications including, but not limited to,
automotive
parts and assemblies, Venetian blinds, and architectural applications. In
particular,
the reflective coating system is particularly useful in architectural
applications, such
as roofing for a residential and/or commercial building. The cured film
imparts the
substrate with aesthetic qualities, protection, and excellent energy
efficiency
properties, which are described additionally below. The coating composition of
the
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present invention is particularly useful as a coil coating composition. A Coil
coating
compositions is typically applied to a metal substrate. The metal substrate is
typically
in coil form, and is unwound prior to application of the coil coating
compositions
thereon to form the cured film. Once the cured film has been formed on the
metal
substrate, the metal substrate is typically wound back up in the coil form.
However, it
is to be appreciated that the coating composition may be used in other
applications,
such as in automotive coatings, without departing from the scope of the
present
invention.
[0015] As set
forth above, the substrate is typically a metal substrate. In
certain embodiments, the metal substrate is further defined as steel. The
steel of the
metal substrate may have a coating disposed thereon. One example of the
coating that
may be disposed on the steel of the metal substrate is an aluminum-zinc alloy.
A
particular example of steel having the coating of the aluminum-zinc alloy
disposed
thereon is Galvalume . The metal substrate may also comprise steel having a
zinc
coating disposed thereon, which is commonly referred to in the art as
"galvanized"
steel. Further, the metal substrate may comprise steel, such as stainless
steel.
However, it is to be appreciated that any metal or alloy may be used as the
metal
substrate for purposes of the present invention. It is to be further
appreciated that the
substrate is not limited to the metal substrate; the substrate may comprise
any
material, such as plastics, glass, fiber, etc.
[0016] The
coating composition is substantially free from chromate. The
terminology "substantially free", as used herein in reference to the chromate,
means
that the amount of chromate present in the coating composition is sufficiently
low so
as to avoid any undesired adverse impact with respect to a toxicity of the
coating
composition. Typically, the amount of chromate present in the coating
composition is
less than 5, typically less than 0.5, more typically less than 0.1, and most
typically
zero, percent by weight based on the total weight of the coating composition..
[0017] The
coating composition comprises a resin. The resin is typically self-
crosslinking. Alternatively, the coating composition may further comprise a
cross-
linking agent reactive with the resin. The resin may be selected from the
group of
acrylics, epoxies, fluorocarbons, polyesters, siliconized polyesters,
plastisols,
urethanes, and combinations thereof. In addition, the resin may be a
solventborne
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resin or a waterborne resin. The resin is typically present in the coating
composition
in an amount of from about 40 to about 95, more typically from about 40 to
about 55
percent by weight based on the total weight of the coating composition.
[0018] In one
embodiment of the present invention, the resin is an acrylic
resin. As set forth above, the acrylic resin may be a solventborne resin or a
waterborne resin. For the solventborne resins, the solvent may be, for
example,
methyl n-Amyl ketone, n-butyl acetate, t-butyl acetate, xylene, acetone, and
the like.
The water or solvent is typically present in the coating composition in an
amount of
from about 25 to 45 percent by weight based on the total weight of the coating
composition. In one particular embodiment of the present invention, the resin
is a
waterborne acrylic resin. The waterborne acrylic resin is typically self-
crosslinking.
[0019] The
acrylic resin typically has a number average molecular mass, Mn,
of from greater than zero to about 500,000 g/mol. The acrylic resin typically
has a
weight average molecular mass, M, of from about 200 to about 500 g/mol.
Suitable
acrylic resins may be formed by reacting acrylic acid with an alcohol to form
a
carboxylic ester. The carboxylic ester may combine with itself or other
monomers to
form the acrylic resin, which may be a homopolymer.
[0020] As set
forth above, the coating composition may further include the
cross-linking agent. However, as also set forth above, the resin may be self
cross-
linking, in which case no cross-linking agent is required. When the resin is
the
waterborne acrylic resin, the resin is typically self-crosslinking and the
cross-linking
agent is not required. Examples of suitable cross-linking agents for the
purposes of
the present invention include, but are not limited to, melamine resins such as
monomeric and/or polymeric melamine formaldehyde resins, including both
partially
and fully alkylated melamines, such as other methylated melamines, butylated
melamines, and methylated/butylated melamines. The melamine formaldehyde resin
may include alkoxymethyl groups of the general formula:
¨CH2ORI
wherein R1 is an alkyl chain having from 1 to 20 carbon atoms. One specific
example
of the melamine formaldehyde resin suitable for including in the cross-linking
agent,
for the purposes of the present invention, is hexamethoxymethyl melamine,
commercially available under the tradename Resimene , from Solutia of St.
Louis,
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Missouri. The cross-linking agent can also include other aminoplasts
including, but
not limited to, urea resins such as methylol ureas and alkoxy ureas, e.g.
butylated urea
formaldehyde resin. The cross-linking agent may include other cross-linking
agents
known in the art including, but not limited to, epoxy resins, oxazoline
resins, block
isocyanates, methylated urea, butylated urea, methylated/butylated urea, and
combinations thereof When utilized, the cross-linking agent is typically
present in
the coating composition in an amount of from about greater than zero to about
20
percent by weight based on the total weight of the coating composition.
[0021] The
coating composition further comprises an interference pigment.
The interference pigment may be mixed with the other components of the coating
composition in any manner, and order of addition is not significant for the
purposes of
the present invention. For example, the interference pigment may be added
directly to
the resin and the cross linking component under agitation.
[0022] The
interference pigment includes mica. The mica of the interference
pigment has a solar reflective coating disposed thereon. It is to be
appreciated that the
solar reflective coating typically encapsulates the mica. The solar reflective
coating
may be disposed on the mica to form the interference pigment by numerous
methods,
such as by precipitation. It is to be further appreciated that the
interference pigment
may include more than one solar reflective coating layer disposed on the mica.
[0023] The
interference pigment typically transmits at least 60% of all
wavelengths in the range of from 250 to 2,500 nm and less than 50% of solar
energy.
More specifically, the interference pigment is typically translucent and
colorless. As
used herein, the term "colorless" is defined to mean that the interference
pigment does
not have a color. The term "colorless" is further defined to mean that the
absorption
curve for the interference pigment is devoid of absorption peaks in the 400 -
700 nm
range and does not present a tint or hue in reflected or transmitted light
when viewed
under sunlight conditions. The interference pigment is also typically
translucent. As
used herein, the term "translucent" is defined to mean that light passes
through the
interference pigment diffusely. Without intending to be limited by theory, it
is
believed that the colorless translucence of the interference pigment
contributes to a
high solar reflectivity value of the cured film formed from the coating
composition, as
described in further detail below.
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[0024] As set
forth above, the interference pigment includes mica, which has a
solar reflective coating disposed thereon. The solar reflective coating of the
interference pigment comprises an inorganic oxide. The inorganic oxide is
typically
selected from the group of metal oxides, silicon oxides, and combinations
thereof.
The metal oxides may include any metal oxide known in the art. Suitable metal
oxides include, but are not limited to, titanium dioxide, tin oxide, zirconium
oxide,
and combinations thereof The silicon oxides may include any silicon oxide
known in
the art. For example, in one embodiment, the silicon oxides may be further
defined as
silicon dioxide. For ease of addition to the coating composition, the
interference
pigment typically has a particle size of from 10 to 60 m as measured in
accordance
with ISO 1524. It is to be appreciated that the particle size of the
interference
pigment is in reference to the length of the interference pigment because the
interference pigment, like the mica included therein, typically has a platelet
shape,
i.e., the interference pigment is not spherical. Suitable interference
pigments for the
purposes of this invention include those commercially available under the
trade name
SolarflairO, from Merck KGaA of Darmstadt, Germany. The interference pigment
is
typically present in the coating composition in an amount of from greater than
zero to
15, more typically from 2 to 10, percent by weight based on the total weight
of the
coating composition.
[0025] The
coating composition further comprises a metal salt, which
passivates the cured film formed from the coating composition, thereby
providing
resistance to corrosion. The metal salt is a metal salt other than those which
comprise
chromate. The metal salt is typically further defined as zinc phosphate. Zinc
phosphate prevents corrosion of the metal substrate by ameliorating defects in
the
cured film. More specifically, the zinc phosphate converts primary corrosion
products which form in defects of the cured film into a solid, water-stable
compound.
The zinc phosphate also bonds hydroxyl ions to form slightly soluble
compounds,
thereby effectively filling defects in the cured film and preventing corrosion
of the
metal substrate.
[0026] In
certain embodiments, the coating composition further comprises a
second metal salt which, together with the zinc phosphate, provides even
greater
corrosion resistant properties to the cured film formed from the coating
composition
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than the zinc phosphate alone. The second metal salt is a metal salt other
than those
which comprise chromate. It is to be appreciated that the second metal salt
may
include more than one metal salt, i.e., a blend of metal salts. Examples of
second
metal salts suitable for the purposes of the present invention include, but
are not
limited to, calcium metal salts such as calcium phosphate, metal
phosphocarbonates,
metal phosphosilicates, and combinations thereof. The second metal salt has
been
found to act synergistically with the zinc phosphate, thereby improving
corrosion
resistance of the cured film as compared to when zinc phosphate is used alone.
The
metal salt and the second metal salt impart the cured film formed from the
coating
composition with excellent adhesion to the metal substrate and excellent
weathering
properties, with performance substantially imitating that of chromate. The
coating
composition including the metal salt and second metal salt typically has a
life span of
five years attributable to excellent weathering properties. Typically, both
the metal
salt and the second metal salt have a particle size of about 0.5 nm. Each of
the metal
salt and the second metal salt is typically colorless. The metal salt and the
second
metal salt is typically present in the coating composition in a combined
amount of
from 0.01 to 10, more typically from 4 to 10, most typically from 5 to 10
percent by
weight based on the total weight of the coating composition. Additionally, on
an
individual basis, the zinc phosphate is typically included in the coating
composition in
an amount of from 0.01 to 5 percent by weight based on the total weight of the
coating composition, and the second metal salt is typically included in the
coating
composition in an amount of from 0.01 to 5 percent by weight based on the
total
weight of the coating composition.
[0027] It is to be appreciated that, although not required, the coating
composition of the present invention is typically substantially free from
color
pigments other than the interference pigment. Color pigments include
conventional
organic and inorganic color pigments, which are traditionally utilized in
coating
compositions to introduce a particular color to the cured film formed from the
coating
composition. When the coating composition is free from color pigments, the
cured
film formed from the coating composition is sufficiently transparent, which is
desirable for the purposes of the present invention and is objectively
quantified below.
However, it is to be appreciated that the coating composition of the present
invention
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may form a conventional tinted cured film, which has a slight pigmentation,
without
departing from the scope of the present invention so long as the conventional
tinted
cured film is sufficiently transparent, as described in greater detail below.
The
coating composition typically comprises color pigments in an amount of less
than 5,
typically less than 1, more typically less than 0.5, and most typically zero,
percent by
weight based on the total weight of the coating composition.
[0028] The
coating composition may further comprise an additive component.
Typical additive components may include additives selected from the group of
flattening or matting agents, biocides, waxes, surfactants, fillers,
plasticizers,
emulsifiers, texturizers, catalysts, thickeners, adhesion promoters,
stabilizers,
defoaming agents, wetting additives, and combinations thereof. When present,
the
additive component is typically present in the coating composition in an
amount of
from greater than zero to 5 percent by weight based on the total weight of the
coating
composition.
[0029] To form
the cured film on the metal substrate, the coating composition
is applied to the metal substrate. The coating composition may be applied to
the
substrate in any manner known in the art, such as spray application, roll
application,
dipping application, and the like In certain embodiments, the coating
composition is
typically applied to the metal substrate using at least one roller. In one
embodiment, a
first roller transfers the coating composition from an open holding receptacle
to a
second roller, and the second roller applies the coating composition to the
metal
substrate. As alluded to above, it is to be appreciated that other methods of
applying
the coating composition to the metal substrate may be employed.
[0030] Once the
coating composition has been applied to the metal substrate
as described above, the coating composition is typically cured on the metal
substrate
in an oven to form the reflective coating system. The coating composition is
typically
cured in the oven at a temperature of from 700 F to 900 F for a period of
time of
from 20 to 100 seconds. When the oven is heated to the temperature of from 700
to
900 F for the period of time set forth above, the metal substrate typically
attains a
temperature of from 150 to 500 F while in residence in the oven. It is to be
appreciated that although the step of curing the coating composition typically
occurs
in an oven, the coating composition may also be cured using other techniques
and
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equipment, such as an open heat source. Once the coating composition is cured
to
form the cured film, the cured film is cooled to about ambient temperature.
The cured
film on the metal substrate may be sprayed with a coolant, such as water, to
effect the
cooling. Alternatively, the cured film may be cooled to the ambient
temperature
without the use of a coolant.
100311 The cured film typically has a film build of from 0.1 to 0.3 mils.
It is
to be appreciated that the physical properties of the cured film that are
objectively
quantified below are a function of the film build of the cured film. The
physical
properties that are objectively quantified are for the range of the film build
set forth
above, though the physical properties may fall within the described ranges
even when
the film build is greater or less than the film build set forth above. The
cured film of
the reflective coating system, which is formed from the coating composition,
typically
has a solar reflectivity value of greater than 55%, more typically greater
than 65%, as
measured according to ASTM E 1918 and/or ASTM E 903. The cured film of the
reflective coating system typically has an emissivity of greater than 0.75,
more
typically greater than 0.80, at all wavelengths in the range of from 250 to
2,500 nm as
measured in accordance with ASTM E 408 and ASTM C 1371. Further, the cured
film typically has an ultraviolet absorbance of about 70 as measured in
accordance
with ASTM E 903. The cured film of the reflective coating system has a
transparency
of at least 75%, more typically at least 85%, as measured according to ASTM
1746.
It is to be appreciated that although ASTM 1746 is typically utilized to
determine
clarity of a plastic, it can be used to determine transparency of a cured film
as well.
The transparency of the cured film leaves the appearance of the metal
substrate
unobscured while still protecting the metal substrate with the cured film. In
other
words, the metal substrate of the reflective coating system retains a metallic
appearance while having an excellent solar reflectivity and emissivity. In
addition,
the metal substrate of the reflective coating system has excellent corrosion
resistant
properties.
100321 The following examples, illustrating the method of forming the
coating
composition of the present invention, are intended to illustrate and not to
limit the
invention.
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EXAMPLES
[0033] A coating composition is prepared by conventional loading and
mixing
procedures. In a first example, a base composition is prepared by adding
ammonia to
an acrylic resin to form a mixture. The pH of this mixture is adjusted to
about 8.5.
The remaining components, which are listed in the table below, are then added,
thereby yielding the base composition including the following components,
wherein
the corresponding weight percentage of each component in the base composition
is
based on the weight of the base composition prior to the addition of a metal
salt:
Component Wt. %
Resin 93.53
Ammonia 0.04
Solvent 0.99
Interference Pigment 1.98
Deionized water 0.99
Additive A 0.99
Additive B 0.99
Additive C 0.49
[0034] Resin is a self-crosslinking waterborne acrylic resin,
commercially
available from BASF Corp. of Florham Park, NJ.
[0035] Solvent is butyl carbitol.
[0036] Interference pigment comprises mica which has a metal oxide
coating
disposed thereon as the solar reflective coating and is commercially available
from
Merck KGaA of Darmstadt, Germany.
[0037] Additive A is a defoamer.
[0038] Additive B is an associative thickener.
[0039] Additive C is a biocide.
[0040] Various metal salts are added to the base composition to form the
coating composition. The various metal salts, and resulting properties of
cured films
formed from coating compositions including the base composition above and the
various metal salts, are described below. The coating composition is then
applied
onto a Galvalumee substrate to form the cured film having a thickness of from
about
0.1 to 0.3 mils.
[0041] Tests are conducted on cured films formed from samples of the
coating
composition including the various metal salts to determine corrosion resistant
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properties as measured by an ASTM B117 salt spray test. Corrosion resistant
properties are considered a "pass" when the creep from the scribe is about
1/16 in. or
less, "borderline" when the creep from the scribe is about 1/8 in. to about
1/16 in., and
a "fail" when the creep from the scribe is greater than 1/8 in.
[0042] The following samples (Samples 1-A through 5-A) illustrate the
instant
invention and use a combination of metal salts. In particular, Metal Salt B is
included
in each of the samples in a weight percentage of 2.5% of the total weight of
the
coating composition, and the other metal salts are varied in the amounts
listed in the
table, which amounts represent percent by weight based on the total weight of
the
coating composition.
Component Sample 1-A Sample 2-A Sample 3-A Sample 4-A Sample 5-A
Metal Salt A 2.5
Metal Salt B 2.5 2.5 2.5 2.5 2.5
Metal Salt C 2.5
Metal Salt D 2.5
Metal Salt E 2.5
Metal Salt F 2.5
ASTM B117 Pass Pass Pass Pass Pass
[0043] Metal Salt A is a calcium phosphate commercially available from
Halox of Hammond, IN.
100441 Metal Salt B is a zinc phosphate commercially available from
Halox.
[0045] Metal Salt C is a calcium-enriched silica commercially available
from
Halox.
[0046] Metal Salt D is a mixed metal phosphocarbonate commercially
available from Halox.
[0047] Metal Salt E is a mixed metal phosphocarbonate commercially
available from Halox.
[0048] Metal Salt F is a mixed metal calcium phosphosilicate
commercially
available from Halox.
COMPARATIVE EXAMPLES
[0049] The following comparative samples represent comparative examples
of
cured films formed from coating compositions that are similar to the coating
compositions of the instant invention, but include a single metal salt rather
than a
combination of metal salts. Again, tests are conducted on cured films formed
from
H&H File: 065241.00139
13
CA 02691630 2014-04-04
=
WO 2009/045267
PCT/1.152008/010738
Attorney Docket: IN-6401
samples of the coating composition including the various metal salts to
determine
corrosion resistant properties as measured by an ASTM B117 salt spray test.
Corrosion resistant properties are considered a "pass" when the creep from the
scribe
is about 1/16 in. or less, "borderline" when the creep from the scribe is
about 1/8 in. to
about 1/16 in., and a "fail" when the creep from the scribe is greater than
1/8 in.
Comparative Comparative Comparative Comparative Comparative Comparative-
Component Sample 1 Sample 2 Sample 3 Sample 4
Sample 5 Sample 6
Metal Salt A 5
Metal Salt B 5
Metal Salt C 5
Metal Salt D 5
,Metal Salt E 5
_Metal Salt F 5
ASTM BI 17 Borderline Borderline Fail Fail Fail -
Fail
[0050] As is clear, when comparison is made between the
samples that
represent the present invention and the comparative samples, enhanced
corrosion
resistance is achieved when a combination of metal salts, including the zinc
phosphate
and a second metal salt. This is even the case when comparison is made between
samples of the present invention and the comparative sample including only
zinc
phosphate, with the metal salt present in the respective samples at the same
weight
percentage based on the weight of the coating composition.
[0051]
The scope of the. claims should not be limited by the preferred
embodiments set forth in the examples, but should be given the broadest
interpretation
consistent with the description as a whole.
=
